The radiation area interlock system at IUCF

The high radiation areas at IUCF consist of three accelerator rooms and five target rooms. A redundant-logic interlock system is used to prevent accidental entry into these rooms when beam is present. This system requires that an area must be both cleared and selected before beam can be admitted. Clearing is performed by pushing, in order, a series of switches placed strategically in the room to be cleared. This provides assurance that a thorough visual inspection has taken place. Flashing amber lights and a klaxon (interrupted tone) accompany this operation. If any door to the area is opened during or after clear, the operation must be repeated. Selection is done by pushbutton in the control room. After an area has been both cleared and selected, a steel shutter moves out of the beam path and operator-controlled beam stops are enabled. Beam can now be admitted. The system also takes account of bending magnet currents, radiation levels and vacuum valve status. A number of logic fault conditions are defined to detect loss of redundancy or mechanical/electrical failure. All of the active circuitry is located in the radiation-free control room; logic functions are implemented in industrial high-threshold logic, noted for its reliability and trouble-free operation